Advances in communication infrastructures and protocols have allowed standard computing devices to become valuable communication tools. Computers communicate with each other, and with other electronic devices, over networks ranging from local area networks (LANs) to wide reaching global area networks (GANs) such as the Internet. Other electronic devices have experienced similar transformations, such as mobile phones, personal digital assistants (PDAs), and the like. Today, these wireless devices are being used for a variety of different types of communication. For example, while the analog mobile phone was traditionally used for analog voice communications, the present-day mobile phone is a powerful communication tool capable of communicating voice, data, images, video, and other multimedia content. PDAs, once the portable calendaring and organizational tool, now often include network communication capabilities such as e-mail, Internet access, etc. With the integration of wireless and landline network infrastructures, information of all types can be conveniently communicated between wireless and landline terminals.
To facilitate effective communication over such networks, many new protocols have been developed. One particularly popular and promising protocol that allows digital multimedia to be communicated to and from mobile and landline computing devices is the Session Initiation Protocol (SIP). SIP is a signaling protocol that assists digital devices in establishing end-to-end multimedia sessions. SIP provides features that resemble those provided by the Public Switch Telephone Network (PSTN) as well as Internet protocols such as Transmission Control Protocol/Internet Protocol (TCP/IP) and Hypertext Transfer Protocol (HTTP). SIP operates similarly to HTTP, in that it is a text-based message protocol operating on a well-known network port. From the terminal's perspective, SIP is different than HTTP because the terminal includes a listening process to be notified of incoming communications. In contrast, a web browser utilizing HTTP is purely a client, i.e., the browser initiates connections to listening servers at the user's request, and does not listen for incoming connections.
For some network communications, such as pure SIP and IP multimedia subsystems (IMS) implementations, the user equipment may provide different functionalities concurrently. For example, one application may allow the user to make multimedia calls, while another enables other users/servers to subscribe to the user's location information. However, in order for multiple applications to be used in this manner, the terminal must determine which application an incoming message should be directed to. One manner of achieving this goal is to provide a SIP stack for each of the different applications operating at the terminal. This, however, is inefficient and utilizes a great deal of resources. Another manner in which this could be effected is to distinguish applications by different port numbers. However, this is not possible with IMS, as the port number must not be changed by the SIP stack, as it is pre-assigned by the underlying IPSec Security Association.
Accordingly, there is a need in the communications industry for a manner of effectively identifying the appropriate application in a multi-application environment to which incoming messages should be directed. The present invention fulfills these and other needs, and offers other advantages over the prior art.